Understanding the Difference Between Acute, Subacute and Chronic Back Pain
Many physicians distinguish acute from subacute and chronic back pain by the length of time a patient has been symptomatic. According to this approach, acute pain resolves in 6 weeks or less, subacute pain between 6 weeks and 3 months, and chronic pain continues beyond three months, which is considered average healing time for a back strain. However, research suggests the picture is not that simple. According to a group in Denmark, the problem with relying solely on timelines is that most back pain, including so-called chronic pain, is recurrent as opposed to being intractable (Kongsted et al., 2016). This is particularly true for non-specific back pain: pain that is not linked to an identifiable physical pathology. Most back pain complaints fall into this category: about 85% according to most sources (Waddell, 2004).
Complicating matters further, sources disagree as to what symptoms constitute a back strain. Pain is subjective: what feels severe to one patient might be water off a duck’s back to the next. Where do physicians draw the line? Should the determining factor be whether the pain is disabling enough to warrant a primary care visit? Should time off work factor in? What about physical exam findings? This should provide an answer since back pain is to some extent a physical condition.
Once again, there are complicating issues. For example, a test for lumbar flexion should identify patients with severe spine pathology or disk prolapse. It does. However, lumbar flexion is not a sensitive test for spinal infection, inflammatory disease or metastases, all of which cause severe back pain (Waddell, 2004). Physical exam can help to determine disability, which is the amount back pain interferes with normal daily function, also called activities of daily living (ADLs). Tests that evaluate walking speed and distance, ability to climb and descend stairs, and standing up from a seated position are quick and inexpensive ways to determine how much back pain is interfering with a person’s ability to work, recreate and socialize.
This brings us back to the issue of acute, subacute and chronic pain, and how to rate the pain itself. Dr. Gordon Waddell, an orthopedic surgeon and leading authority on back pain, suggests that the best way to rate a patient’s level is to ask them, using a visual analog scale (2004). For example, on a 0-10 scale with 10 being extreme pain and 0 no pain at all, how intense is the pain at its worst and on average?
In terms of the progression from acute pain to chronicity, Kongsted and colleagues (2016) suggest categorizing pain into different trajectories to guide treatment, based on intensity, variability and the change pattern. Intense back pain would garner a rating of 6 out of 10, while minor pain would rate 0 to 1. In terms of variability, the researchers divide patients into subgroups of single-episode pain, episodic pain (separated by periods of months), fluctuating pain (no periods of no pain) and persistent pain (pain 4 or more days per week that stays at the same level). A change in the pain over time is also important: is the pain gradually improving or getting worse over time?
Most experts in the pain field agree that chronic pain rarely resolves completely, so the goal is management of pain rather than becoming pain-free. Since the objective of classifying back pain is to guide treatment, it seems that a system reflecting the character and course of pain over time is more relevant than subdividing patients according to a somewhat arbitrary timeline. In addition, educating patients about the subjective nature of pain, and the way pain progresses over time can lead to more realistic expectations about treatment outcomes.